the reduced diameter base is the heel. It allows the bullet diameter to be the same as the case it is loaded in. 22LR bullets are heeled bullets.

__________________
Good intentions will always be pleaded for any assumption of power. The Constitution was made to guard the people against the dangers of good intentions. There are men in all ages who mean to govern will, but they mean to govern. They promise to be good masters, but they mean to be masters.
--Daniel Webster--

A left over from black powder days when the chamber size dictated the case size and they wanted the bullet to be the same diameter. Heeled bullets in modern ammo is very rare now because the improved powders obviates the need for the larger diameter bullet.

Negative to the heeled bullet is accuracy with higher velocity bullets, it's easier with a bullet that has one diameter for its entire body length.

__________________
Good intentions will always be pleaded for any assumption of power. The Constitution was made to guard the people against the dangers of good intentions. There are men in all ages who mean to govern will, but they mean to govern. They promise to be good masters, but they mean to be masters.
--Daniel Webster--

It's easy to drill a straight through chamber, and most early cartridges were rimmed. So a chamber was simply a hole the size of the cartridge. It's easy to cast lead into any reasonable shape, so by making the bullets fit both the inside of the case (where the heeled portion is) and the chamber (the portion with the band in the picture), which was the same diameter as the outside of the case, the manufacture of the chamber was much simplified.

When velocities jumped with the advent of smokeless powder, jacketed bullets started becoming more common and heeled bullets began to fall out of use for several reasons. One reason is that it's a pain to make a jacketed bullet with a heel, so the bullet was made to fit inside the case, and the chamber was tapered down in front of the case mouth to fit the bullet diameter. In addition, in rimless cartridges, the chamber had to provide a means to headspace the cartridge, so more complicated chamber shapes became commonplace. So it was no longer an issue to make a chamber that wasn't a straight through hole, and the higher velocities and other issues made heeled bullets less attractive.

The change away from heeled bullets also helps explain the apparent disconnect between some caliber designations and the actual bullet diameters commonly associated with them. For example, the .38 special uses a .357" diameter bullet. The reason is that originally, .38 revolvers used heeled bullets, with a nominal bullet diameter identical to the OUTSIDE case diameter. Later, when heeled bullets fell out of common use, .38 revolvers transitioned to non-heeled bullets with a nominal bullet diameter identical to the INSIDE case diameter which was about .357". Same deal with .44 revolvers which typically use .429" bullets.

.22WMR bullets are not heeled. .22WMR rounds can't be shot in .22LR guns because the cartridges won't chamber (they're too long and larger in diameter).

In addition, .22WMR bullets are slightly larger than .22LR bullets and are jacketed which makes them a less than ideal fit for a .22LR bore even if one were to modify a .22LR chamber to accommodate the .22WMR cartridges.

Finally, the .22WMR cartridge is considerably more powerful than the .22LR which would make it unsafe in semi-auto actions designed for the .22LR and possibly in other actions as well--again, even if one were to modify the chamber so the rounds would chamber.

The change away from heeled bullets also helps explain the apparent disconnect between some caliber designations and the actual bullet diameters commonly associated with them. For example, the .38 special uses a .357" diameter bullet. The reason is that originally, .38 revolvers used heeled bullets, with a nominal bullet diameter identical to the OUTSIDE case diameter. Later, when heeled bullets fell out of common use, .38 revolvers transitioned to non-heeled bullets with a nominal bullet diameter identical to the INSIDE case diameter which was about .357". Same deal with .44 revolvers which typically use .429" bullets.

Another example illustrating the discrepancy is from the world of black powder revolvers. A .44 caliber BP revolver takes a lead ball that starts out around .452" to .454" in diameter, and shaves it as you press it into the cylinder. The conversions that are sold to allow .44 caliber BP revolvers to fire modern ammo use .45 Long Colt ammo.

The BP designation of .44 caliber was based on the bore, while the .45 Colt designation was based on the groove diameter.

Gets even more interesting when you try to explain why a ,410 shotgun is a bore size and not a caliber and why gauges are smaller numbers as the bore gets larger. Takes a lot of wading through the swamp to get it all straight in your head and nobody can get all of it.

__________________
Good intentions will always be pleaded for any assumption of power. The Constitution was made to guard the people against the dangers of good intentions. There are men in all ages who mean to govern will, but they mean to govern. They promise to be good masters, but they mean to be masters.
--Daniel Webster--

.22WMR bullets are not heeled. .22WMR rounds can't be shot in .22LR guns because the cartridges won't chamber (they're too long and larger in diameter)... In addition, .22WMR bullets are slightly larger than .22LR bullets and are jacketed which makes them a less than ideal fit for a .22LR bore...

Prof Young... FWIW there is actually a lower-powered, low-recoil .22WMR/.22Mag alternative- the .22 Winchester Rimfire (.22WRF). The .22WRF is the .22WMR's slightly shorter-cased parent cartridge; it does NOT use a heeled bullet and can be used in most .22WMR firearms, although it may fail to cycle some semi-autos properly.

However, unlike using .22LR in a "convertible" revolver, there's usually little or no practical cost savings from using .22WRF; it's also generally hard to find because it's obsolescent. Demand is low enough that IIRC it was briefly dropped from commercial production a few years ago before being reintroduced by CCI and Winchester.

__________________
"Smokey, this is not 'Nam. This is bowling. There are rules... MARK IT ZERO!!" - Walter Sobchak

Last edited by carguychris; December 10, 2012 at 04:26 PM.
Reason: info added...

Which doesn't begin to explain the .38-40 cartridge from the 1880's, since the bullet has a .40 caliber / 10mm diameter.

How the heck did that happen?

They wanted a bullet with similar flight characteristics of the 44-40 but the 200 gr 44 caliber bullet with 40 gr of black powder was considered too stout for some shooters. drop 20 grains and reduce bullet diameter to .401 instead of the .427 of the 44-40 and marketing steps in with a smaller number of 38. I have never ever found a good solid reason for calling a 40 caliber bullet a .38 because going by convention back then they should have named it the .416 or the 41 or the 42 because of the .416 neck diameter of the case. Never ever try to follow the logic of marketing, it will drive you nuts.

__________________
Good intentions will always be pleaded for any assumption of power. The Constitution was made to guard the people against the dangers of good intentions. There are men in all ages who mean to govern will, but they mean to govern. They promise to be good masters, but they mean to be masters.
--Daniel Webster--

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